1. Field of the Invention
The present invention relates to a monitoring device for a programmable controller, the monitoring device being configured to display an operation state of the programmable controller that executes a program described to include a plurality of steps each indicative of an individual control process and a transition indicative of a transition condition between the plurality of steps.
2. Description of Related Art
Conventionally, as a programming language for a programmable controller that controls a facility such as a machine tool, a ladder logic (a ladder language), a sequential function chart (a SFC language), a function block diagram (a FBD language), and the like have been known, as prescribed in the IEC61131-3 standard. Among them, the SFC language is a format that describes a flow of an individual control process like a flowchart. Since the SFC language has high clarity, the SFC language has been widely used in recent years.
In the meantime, a program described by the SFC language is described on the presumption that a plurality of steps each indicative of an individual control process is executed sequentially from the top. Accordingly, in a case where execution of the program described by the SFC language stops halfway due to some troubles while a programmable controller is executing the program described by the SFC language, it is difficult to restart the control processes from a step at which the troubles occur, at the time of reactivation after troubleshooting.
In view of such problems, the applicant of the present application has proposed a programmable controller that can appropriately reactivate a program described by the SFC language after the program stops halfway (see Japanese Patent Application Publication No. 2008-97079 (JP 2008-97079 A)).
However, the programmable controller described in JP 2008-97079 A assigns a ladder program described by the ladder language to each transition indicative of a transition condition between steps, and the ladder program is constituted by combining a halfway activation flag that is turned on when the ladder program is reactivated, an activation condition of a step just before each transition, and the like. Therefore, it takes time for a programming operation of the ladder program. Further, depending on a content of the troubleshooting, it may be necessary to restart the control processes from a step different from the step at which the troubles occur. However, in such a case, it is difficult to restart the control processes from a given step. Thus, the programmable controller described in JP 2008-97079 A left room for improvement.